2012 Atlantic Hurricane Season Birdseye Discussion #160

...THURSDAY NOVEMBER 15 2012...6:55 AM EDT...Tropical activity in the Atlantic remains calm as we enter the final two weeks of hurricane season. The GOES satellite derived 200 mb wind barbs in the atmospheric features chart are currently not functioning. The upper-level features in the chart are therefore marked based on the upper-level wind barbs from http://www.goes.noaa.gov/WINDS/fullIREast.htm.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0729Z-released HPC analysis.

...MID-LATITUDES DISCUSSION...P1...Surface frontal gale over Greenland and surface frontal low over Canada's Hudson Bay...both mentioned in paragraph P1 of the previous discussion...have merged into one large surface low east of Greenland that has exited the picture from the top-center. A very lengthy surface cold front still extends from the exiting surface low...now stretched across the western Atlantic and Gulf of Mexico. Just before merging with the exiting surface low...the surface frontal low over Canada's Hudson Bay has left behind an east-west front across southern Canada seen in the top-left of the above charts. Major upper trough covering North America persists. Western convergence of the major upper trough continues to support strong surface ridging across the US. Eastern divergence of the major upper trough continues to support a W Atlantic surface low that has moved NNE across Bermuda...and is currently 1015 mb while positioned just NE of Bermuda.

P2...NE Atlantic upper trough has exited the above charts from the top-right except for a cut-off upper vortex that has developed midway between the Azores and Canary Islands in association with locally maximal cool air advection of 997 mb surface frontal depression that formed NE of the Azores during the previous discussion. This depression has weakened to 1002 mb while whirling cyclonically beneath the non-divergent environment directly under the upper vortex.

...TROPICAL BELT DISCUSSION...P3...Upper ridge axis over the central tropical Atlantic has been expanded northward toward Greenland via warm air advection ahead of the W Atlantic-to-Gulf of Mexico surface front and 1015 mb W Atlantic surface low both mentioned in paragraph P1. Upper divergence west of this upper ridge and east of the paragraph P1 major upper trough has supported the formation of a new eastern Caribbean surface trough. Upper convergence east of this upper ridge axis supports the north Atlantic surface ridge (currently greater-than-1032 mb) mentioned previously in paragraph P1 of discussion #159.

P4...Cut-off upper trough NW of the Cape Verde Islands persists. Expansive upper divergence east of this cut-off upper trough supports a wide area of t-storm clouds. Surface troughing formerly supported by this upper divergence continues to be steered westward by the paragraph P3 north Atlantic surface ridge. As a result...the surface troughing is now located midway between the Cape Verde Islands and Lesser Antilles...and has entered the unfavorable western convergence on the back side of the cut-off upper trough that is keeping the surface troughing inactive.